Pyrolysis device



March 16, 1965 P. F. VARADI ETAL PYROLYSIS DEVICE Filed Feb. 25, 1963 s g 9 18/7 23 L H 224 25 5a .a if? 1 2 32 26 CARRIER GAS SUPPLY United States Patent Ofi ice 3,l?3,752 Patented Mar. 16, 1965 3,173,762 PYRGLYSIS DEVIQE Peter F. Varadl and Kitty S. Ettre, Stwrford, Q6333. assignors to Machiett Laboratories, Incorporated, Springdale, (101121., a corporation of Connecticut Filed Feb. 25, 1963, Ser. No. 269,739 4 Claims. (Cl. 23---25 This invention relates to a pyrolytic instrument and particularly to a device for use in the pyrolysis of a material to be directed as a gas or vapor into apparatus such as a gas chromatography system or the like.

A gas chromatography system is an analytical tool used for the analysis of volatile materials. One type of gas chromatography system is fully shown and described in copending application Serial No. 184,881, filed April 3, 1962, by Peter F. Varadi. With such a system it is possible to separate and analyze ready sample mixtures, to study certain chemical reactions, or to investigate the behavior of diiferent substances under certain conditions. To accomplish this, the reaction products of the materials or substances being investigated or studied are purged with the help of an inert gas directly into the gas chromatography system.

The degradation of complex organic molecules is a classical method used in organic chemistry for structure identification and one of the most frequently used techniques is the pyrolysis of the material in an inert atmosphere, under controlled circumstances. In this technique, the original material is degraded to specific volatile compounds by a pyrolysis device which is attached directly to a gas chromatograph. A sample of the material to be studied is pyrolyzed in an inert atmosphere, which atmosphere may be the carrier gas used in the gas chromatograph, and the vapor products resulting from such pyrolysis of the sample are purged instantaneously as a plug into the chromatographic system by the carrier gas flow.

Two dilferent types of pyrolysis devices are generally utilized, those using flash pyrolysis and those using reac tion chambers. In the flash pyrolysis method, the sample to be pyrolyzed is placed on or in a filament which is heated rapidly to the desired temperature whereupon the vapor breakdown products are swept by carrier gas into the gas chromatograph for subsequent analysis. With this method it is dilficult to analyze material which is in solid form since it is generally preferable to first dissolve the material in order to coat it on the filament. Thus, this pyrolysis process may not give the true picture because the breakdown of the dissolved form of the original compound is often not identical to that of the undissolved solid molecule. Furthermore, the breakdown products of the solvent may also appear in the gas chromatograph. When attempting pyrolysis of solid matter, the heating of the sample is not instantaneous. The sample goes through a wide temperature scale before reaching the desired temperature, thereby undesirably affecting the whole pyrolysis process. Thus the result of study by flash pyrolysis does not reflect true pyrolysis at a given temperature.

Some of the above disadvantages of flash pyrolysis are overcome in the second technique wherein pyrolysis is performed in a reaction chamber, usually a stainless steel tube, where the sample may be introduced directly at the temperature of the desired pyrolysis. In prior art types of reaction type devices, the steel tube, containing the sample and an iron core, was inserted in a reaction furnace and, after pyrolysis, was withdrawn by means of a magnet. This method worked well only at relatively low temperatures, up to about 430 C. At higher temperatures it could not be used because of the iron core. Furthermore,

at higher temperatures the stainless steel tube often caused catalytic effects upon the pyrolysis. In some known devices only metallic materials could be pyrolyzed, thus rendering the devices useless for chemical decomposition of plastics, for example.

It is the primary object of this invention to eliminate the above and other disadvantages of the prior art. The presently described device further provides additional advantageous features such as ofifering the possibility of series analyses Without opening the chamber for replacement of samples or removal of sample-carrying boats. It comprises an open-ended hollow cylinder or chamber having one end connected into a gas chromatography system or other analyzing system and having its other end connected into a supply of carrier gas which may or may not be the same supply of gas as used in the chromatography system. The chamber or tube comprises a main body portion partly of glass or metal and partly of material which is highly heat resistant, such as quartz or ceramics. The quartz part of the tube is adapted to be placed in a combustion type furnace. Extending from one side of the glass tube is a hollow arm within which are placed a number of boats carrying samples of materials to be pyrolyzed. The interior of the arm communicates with the interior of the glass tube so that an external magnet may be used, in conjunction with internal magnetic means, to move the boats one at a time into the glass tube, from which they may be urged into the quartz tube where the samples are pyholyzed. A second divergent arm is connected to the glass tube for receiving discarded boats, whereupon other boats may be successively moved into the glass tube without opening the chamber.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is an elevational view of a pyrolyzing device embodying the invention and showing the major portion of the device in vertical section; and

FIG. 2 is a diagrammatic view of the device of FIG. 1 illustrating the method of moving samples into and out of the reaction furnace area.

Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the views, the device shown in FIG. 1 embodies a pyrolysis chamber 1% which comprises a length of glass tubing 11 on one end of which a suitable fitting such as flanged metal fitting 12 is mounted by a suitable glass-to metal seal 13. To fitting 11 is connected one end of a tubing l4 which is provided with means for imparting flexibility to the tubing such as sections 15 and 16 shaped as bellows, or by sections of deformable plastic tubing. Tubing 14 may be of metal or other selected material impermeable to gas or vapor and is connected in a vacuumtight joint to the flange 17 of fitting 12 by any suitable means such as, for example, by positioning an G-ring gasket 18 of neoprene or the like between flange 17 and the outer surface of a flange 19 formed on the end of tubing 14, which dan es and gasket are held firmly together in a vacuum-tight seal by suitable means such as bolts or the like.

Chamber 10, in addition to glass tube 11, includes a quartz tube 29 Which at one end is mounted coaxially onto the end of glass tube 11 by a suitable graded seal 21 in any manner known to the art. Quartz tube 20 has its opposite end portion 22 sealed by another graded seal 2.3 to a short glass tube 24, to which a metal exit port 25 is sealed by a glass-to-metal seal. The exit port 25 may take any form suitable for attachment or" the pyrolysis device, by means such as a sampling valve (not shown), to a gas chromatograph or other apparatus with which the device is to be used.

caravan Enclosing at least a portion of the quartz tubing 24 is a combustion type furnace 26 to which electric current is supplied by suitable conventional low voltage transformer means (not shown) regulated by a variable transformer 27 in a manner Well known in the art. 'The temperature of the furnace in the area where boats are placed is sampled by a thermocouple 23 and transmitter for measurement to a millivoltmeter 29, preferably calibrated in centigrades.

The furnace should have a definite relationship to the length of the individual boats so that the end portions of the furnace will not produce undesirable deposition of the highly volatile decomposition products on the cooler portions of the quartz tubing. In accordance with this invention it has been found that the furnace should not be more than about 15-20 times longer than the boats. Likewise, in order to provide successful pyrolysis, the furnace should not be shorter than about twice the lentgh of the boats. An efficiently operated furnace has a length of about 2 /2 inches for use with boats about inch in length. Furthermore, the heat capacity of a boat should not be such as will alter the temperature of the furnace when placed therein.

It has also been found advisable to provide means for slightly elevating the temperature of the portion of the chamber which extends beyond the furnace on the side thereof nearest the gas chromatograph.

This may be done, for example, by means of a surrounding heatable metal shield or tubulation 59 through which sufficient electric current is introduced to raise the temperature of this area of the chamber above ambient temperature to avoid deposition on the chamber walls of the decomposition products of the samples. Other heating means for this purpose may alternatively be provided such as shaping the metal exit port 25 so that it has a portion (not shown) which extends as a shield up to the side of the furnace, or by use of a conductive tape or wire encircling this area of the chamber.

The main glass tube 11 is provided with two integral divergent arms 30 and 31, arm 30 extending angularly 'rearwardly and downwardly from a point adjacent the end of tube 11 which is attached to quartz tube 20 and being supported adjacent its other end by a glass Web 32. The other arm 31 depends substantially vertically from main tube 11, and the interiors of both arms communicate directly with the interior of the main tube 11.

Arm 30 provides means whereby a number of ceramic boats 33 (FIG. 2) may be stored for subsequent pyrolysis of samples carried by the boats. For example, each boat 33 may carry a diflzerent sample of chemical, organic or inorganic plastic or other material which is to be analyzed in the gas chromatograph, which samples may be in solid form or may be painted on the boats, or otherwise carried by the boats as desired.

Behind each boat 33 is positioned a short metal rod 34 or other suitably shaped piece of metal easily subject to an external magnet which is to be used for guiding the boats one at a time into the quartz tube 29.

Within the main glass tube 11 is located a relatively long metal rake 35 by means of which a boat in the entrance to quartz tube 20 may be pushed into the por tion of tube 20 which lies within furnace 26. The rake 35 may be manipulated by an external magnet to urge the boat far enough into quartz tube 2t) where the boat will meet a stop 36 which is provided to accurately locate a boat in substantially the center of the furnace.

The stop 36 is preferably a short integral projection or low wall-like barrier extending inwardly from the inner wall of tube 20, but may take other forms if desired.

To withdraw a boat after the sample thereon has been pyrolyzed, the rake 35 is lifted over the boat so that an angled end portion or book 37 thereon will hook onto the boat, whereupon the rake provides means by which the boat may be pulled back into glass tube 11 where it is allowed to fall into arm 31. Arm 31 thus provides a receptacle for discarded boats as well as for the short rods or plugs 34.

The free end of each arm 30 and 31 is sealed by a suitable cap 38 and 39 or other removable closure so that boats may be easily inserted in and removed from the device. The caps should, of course, provide an airtight seal so that external atmospheres will not be introduced into the device.

In the assembly of the presently described pyrolysis device into a gas chromatograph or other system with which it is to be used, the pyrolysis chamber is preferably first inserted into the electrical heating unit to the extent necessary to locate the stop 36 at the proper position in furnace 26. The port 25 is then connected into the chromatograph by means of a suitable valve (not shown). At this point, the metal rake is inserted into the open end of glass tube 11 and the flexible tube 14 is then attached to fitting 12. The opposite end of flexible tube 14 is thereafter attached either directly into the outlet valve (not shown) of the carrier gas supply 40 (FIG. 1) or into a portion of the gas chromatograph which receives gas from supply 40 whereby, when the valves are opened, the carrier gas will flow into flexible tube 14 and thence through the pyrolysis chamber 10 into the gas chromatograph.

In operation of the device, with the above-mentioned valves closed, cap 38 is removed and boats 33 are placed in arm 30 with a short metal rod 34 being positioned behind each boat. Each boat carries a sample which .is to be pyrolyzed in the pyrolysis chamber and subsequently analyzed in the gas chromatograph. When all the boats are positioned in the arm 30, cap 38 is replaced to seal the entrance to arm 34). With cap 39 in place sealing the lower entrance to receptacle 31, the valves are opened to purge the unit with carrier gas from supply 40, thus expelling all other atmosphere from the device. When thus purged, the device is properly prepared for the pyrolysis of the samples.

This is accomplished by first heating the furnace 26 to the desired temperature which is intended to relatively quickly or even instantaneously pyrolyze the samples in the boats. Of course, temperatures may be changed with successive boats if desired. After the temperature has been stabilized, the first boat 33 is pushed by means of an external magnet which urges the first metal rod 34 and boat out of arm 30 into the entrance to the quartz tube 29. The small rod 34 is then pulled by the magnet back into glass tube 11 and is allowed to fall into receptacle 31.

Then the rake 35 is operated by the magnet to move the boat into quartz tube 20 until the boat abuts stop 36, which thus places it in the desired position within the furnace. This particular operation must be performed relatively fast so that the sample in the boat will not pyrolyze until the boat is properly positioned in the required temperature area of the furnace. Pyrolysis occurs relatively quickly (usually within less than 5 seconds) and the vapor products are carried into the gas chromatograph by the flow of carrier gas. After the pyrolysis process, the rake 35 is used to remove the boat from the quartz tube 20 and to draw it back into the glass tube 11 until it drops into receptacle 31. Then the procedure is repeated for pyrolysis of the samples in the other boats 33 in arm 3%, all of which samples may be successively pyrolyzed without opening the device.

From the foregoing description it will be apparent that a novel and efiicient pyrolysis device has been provided wherein several samples of any type of volatile material may be successively subjected to pyrolysis without opening the device. It is to be understood, however, that various modifications in the structure shown and described, and in the manner of its use, may be made by those skilled in the art without departing from the spirit of the invention as expressed in the accompanying claims.

3 What is claimed is: 1. A pyrolysis device comprising: an elongated chamber comprising a hollow open-ended glass cylinder and a coaxial hollow cylinder of material highly resistant to heat, said cylinders being joined in. end-to-end relation,

means for connecting the free end of the glass cylinder to a source of carrier gas,

means for connecting the free end of the heat re sistant cylinder to an analyzing system,

a furnace enclosing the heat resistant cylinder,

means for maintaining the furnace at a constant pre-selected temperature,

means for positioning sample-carrying boats within the heat resistant cylinder,

said last-named means comprising barrier means carried by the inner surface of the chamber for restricting inward travel of the boats and for centering the boats Within said furnace.

2. A pyrolysis device comprising: an elongated chamber comprising a hollow open-ended glass cylinder and a coaxial hollow cylinder of material highly resistant to heat, said cylinders being joined in end-to-end relation,

means for connecting the free end of the glass cylinder to a source of carrier gas,

means for connecting the free end of the heat resistant cylinder to an analyzing system,

a furnace enclosing the chamber, the chamber being insertable into one side of the furnace and having a portion thereof projecting out wardly beyond the opposite side of the furnace,

means for heating said outwardly projecting portion of the chamber to a temperature above ambient temperature, and means for positioning sample-carrying boats within the heat resistant cylinder. 3. A pyrolysis device as set forth in claim 1 wherein said boats are each of a predetermined length, and the furnace is of a length of approximately two to twenty times the length of the boats.

4. A pyrolysis device as set forth in claim 1 wherein said boats are each about /s inch in length and the furnace is about 2 /2 inches long.

References Cited by the Examiner UNITED STATES PATENTS 2,382,301 8/45 Dreher 23-253 2,795,132 6/57 Boehme et al 23253 References Cited by the Applicant UNITED STATES PATENTS 1,515,237 11/24 Yensen. 2,336,075 12/43 Derge. 2,371,637 3/45 McDermott. 2,589,391 3/52 Hutchison. 2,593,878 4/52 Haines et al. 2,669,504 2/54 Halvorson et al. 2,905,536 9/59 Emmett et al. 3,028,224 4/62 Ferrari. 3,043,127 7/62 De Ford et al. 3,050,372 8/62 Scott. 3,057,692 10/62 Van Kirk et al.

MORRIS O. WOLK, Primary Examiner. JAMES H. TAYMAN, JR., Examiner, 

1. A PYROLYSIS DEVICE COMPRISING: AN ELONGATED CHAMBER COMPRISING A HOLLOW OPEN-ENDED GLASS CYLINDER AND A COAXIAL HOLLOW CYLINDER OF MATERIAL HIGHLY RESISTANT TO HEAT, SAID CYLINDERS BEING JOINED IN END-TO-END RELATION, MEANS FOR CONNECTING THE FREE END OF THE GLASS CYLINDER TO A SOURCE OF CARRIER GAS, MEANS FOR CONNECTING THE FREE END OF THE HEAT RESISTANT CYLINDER TO AN ANALYZING SYSTEM, A FURNACE ENCLOSING THE HEAT RESISTANT CYLINDER, MEANS FOR MAINTAINING THE FURNACE AT A CONSTANT PRE-SELECTED TEMPERATURE, MEANS FOR POSITIONING SAMPLE-CARRYING BOATS WITHIN THE HEAT RESISTANT CYLINDER, SAID LAST-NAMED MEANS COMPRISING BARRIER MEANS CARRIED BY THE INNER SURFACE OF THE CHAMBER FOR RESTRICTING INWARD TRAVEL OF THE BOATS AND FOR CENTERING THE BOATS WITHIN SAID FURNACE. 